Survival of Species By: Cammie Goodman

Survival of Species You already know that every kind of living thing has adaptations that help it survive. But what if conditions changed? Then some plants and animals might not survive. Some groups of living things may disappear

What is a species? A species is a group of living things that can mate with each other to produce offspring, or young.  Bald eagles make up a species, so do lions. So do humans.  No two living things are exactly alike, but members of a species are a lot like each other.

Long ago, the dinosaurs known as Tyrannosaurus rex made up a species. But today, Tyrannosaurs are extinct, or no longer found living on earth.  When a species become extinct, all its members have died out. An extinct species is gone forever.

 We know about Tyrannosaurs and other dinosaurs only from fossils.  A fossil is the remains or trace of an organism that lived long ago.  People have found fossils of dinosaur bones and teeth.  The picture below shows a Tyrannosaurus rex skeleton. Scientist constructed it using fossil bones.

How Species Survive No species would be alive today if its members could not reproduce.  Recall that when living things reproduce, they make more living things of the same kind.  Lions produce more lions; bald eagles produce more bald eagles and so on.  In animals, the process begins when a male and female of a species mate. It ends with the birth or hatching of offspring.

Every animal or plant comes to the end of its life and dies.  Species survive because their member reproduces.  But suppose that animals of a certain kind die faster than they can produce offspring.  The number of animals of that kind will get smaller and smaller, until the species is extinct.  An endangered species is one that is in danger of disappearing, or becoming extinct.  Events in nature can cause a species to become endangered or extinct. So can human activities.

Events in Nature Affect Species Long before people lived on Earth, species of plants and animals become extinct. Events in nature caused them to die faster than they could reproduce

 Climates changed from warm to cold. Species that could not live in cold places did not survive long enough to reproduce. They became extinct.  Jungles turned into deserts. Jungle species that could not survive in hot, dry deserts became extinct  In some places, floods covered land that had been dry. Species that could not live and reproduce in wet places died out.

 New predators appeared. Animals that could not defend themselves or hide were eaten faster than they could reproduce. These animals’ species died out.  New species appeared that could compete better for resources than existing species. Recall that members of different populations compete, or fight, for the same resources. When a new competing species got too much of a resource, an existing species could become extinct.

Did you know? People hunt tigers, cheetahs, and snow leopards for their fur. Hunting and other human activities endangered these animals.

Here are the top 10 most endangered species, according to World Wildlife Fund: 1. Tiger2. Polar Bear

3.Pacific Walrus 4. Magellanic Penguin

5. Leatherback Turtle 6. Bluefin Tuna

7. Mountain Gorilla 8. Monarch Butterfly

9. Javan Rhinoceros 10.Giant Panda

Scientists know that many species died out at the same time, about 65 million years ago.

Scientists think they died because an object from space crashed on Earth.

 The crash threw huge amounts of dust into the air. The dust blocked out sunlight.  Many plants died because they did not have sunlight to make food.  Then many animals that ate those plants died.  So did animals, such as carnivores, that fed on those plant-eaters.  Dinosaurs and many species became extinct.

Human Activities Affect Other Species Today, events in nature still cause species to die out. But human activities are also putting species in danger.

Hunting can cause a species to disappear.  That is what happened to Carolina parakeets.  These bright-colored birds used to live in Georgia and other southeastern states.  But farmers killed the bird because they ate crops. Farmers shot so many Carolina parakeets that by 1920 the species was extinct

People also destroy habitats.  Recall that a habitat is where a plant or animals lives.  Besides hunting Carolina parakeets, farmers cut down forests where the birds live.  Smaller habitats meant that few birds could survive.  Today, the loss of their habitats puts many species in danger.

People put harmful materials into the environment.  These materials are called pollutants.

Farmers used to spray their crops with a chemical called DDT.

The chemicals killed insects that fed on the crops. Then DDT got into the bodies of animals that ate the insects. When eagles and hawks ate these animals, the DDT got into their bodies

 The DDT made the birds produce eggs with very weak shells.  Many of the shells broke before young birds could hatch.  Some bird species, such as Georgia’s bald eagle, almost became extinct.  Since 1972, it has been against the law to use DDT in the United States.  Other pollutants have put species in danger, too.

Discussion Question: Suppose a species of bird cannot find safe places to build nests. What may happen to that species?